This invention relates to an insulator bushing for high d-c voltage input to be used in an electric precipitator or the like.
In an electric precipitator for electrostatically collecting or separating suspended particles e.g. dirt and dust from a flow of gas or air to be cleaned, one of the essential requirements for performance of a high-efficiency dust collection lies in maintenance of a predetermined high d-c voltage being applied to the electrode. To this purpose, the ordinary insulator bushing for high d-c voltage input has been designed to provide a means to supply therein a flow of sealing gas under pressure which acts to shut off the interior of the bushing aerodynamically from the main flow channel of dust-laden gases passing beneath the insulator bushing in the precipitator. This flow of sealing gas avoids attachment or deposition of dust particles on the inner wall surface of the bushing that may cause surface leakages of current from or short discharges of the high d-c input electrode. With the ordinary insulator bushing described above, however, the problem is that due to a comparatively larger size of a sealing gas guiding member necessary for prevention of short discharges between it and the electrode, a greater quantity of such sealing gas is required for each insulator bushing; and the sealing-gas consumption will become significant particularly in case of modern large multi-stage precipitator systems employing a great number of insulator bushings. And, this problem results also in a considerable increase in cost of accessory equipments for supply of the sealing gas e.g. blowers, heaters, etc.